Method of forming sheet metal.



0. 1. GRUEHN. METHOD 0F FORMING SHEET METAL. APPLlcATxoN mio lune' 1|,19.14.

il, Patented. Jan. 11, 1916.

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OTTO J. GROEHN, OF'DETROIT, MICHIGAN, SSIGNOR TO BRISCOE MANUFACTURINGCOMPANY, OF DETROIT, MICHIGAN, A CORPORATION 0F MICHIGAN.

METHOD OF FORMING SHEET METAL.

Specification of Letters Patent.

Patenten aan. it, raie.

Application led June 11, 1914. l Sera11\To. 844,447."

To all whom it may) concern.'

Be itknownthat I, OTTO J. GROEHN, a citizen of the United States ofAmerica, residing at Detroit, in the county of Wayne and State ofMichigan, have invented certain new and useful Improvements in Methodsof Forming Sheet Metal, of which the following is a specification,referenceV being had therein to the accompanyingl drawings.

The invention relates to the manufacture In the present state' of theart automobile fenders are commonly formed from sheet metal which iscurved in one plane only and may therefore be readily formed from a flatblank withoutv drawing or flowing of the metal. There is, however, ademand for fenders which are concavo-convex in cross section, as well asbeing curved longitudinally in conformity to the wheel but suchconstructions cannot be made by the process commonly used. It ispossible to produce such form by suitable drawing dies, but thisrequires heavy and expensive machinery, and on account of the largenumber of sizes and variations and frequent change inV shape, such aprocess is not a commercial success. The present invention overcomesthese diliculties by the formation of the desired shapes by a rolling or.progressive treatment of lthe blank; and further, by a method ofholding the blank during the rolling or forming action so as to preventbuckling or deformation of any part thereof.

The invention further comprises the supplementing of the progressiveforming step `by die operations for completing the article in certamportions thereof.

nal section showing themanner of rolling and forming sheet metal; Fig. 2is a cross section through a machine 1n which the metal is rolled; Fig.3 is a section showing the manner of die-fashioning portions of theblank; Fig. 4 is a view similar to Fig. TL-showing ,a modifiedconstruction; Fig. 5

` 1s a cross section through the blank before .the following operation;and Fig. 6 is a j plan view of the blank.

In forming-of larticles from. flat sheet metal vblanks so as to producewarped or transversely-curved surfaces, it is essential to draw orelongate certain portions of the blank, or to contract or-upset otherportions.

With relatively light gage sheet metal `it is difficult to avoid thewrinkling of the portions of the blank which are subjected tocompression stresses, and also to prevent distorting of the blank by thedrawing stresses. To take a specific instance, a wheel fender which iscurved longitudinally. substantially concentric with the wheel and4transversely to lhave'- a convex cross section,

the longitudinal center of the blank mustl be drawn or expanded whilethe marginal -portions will be subjected to compression stresses.Furthermore, the drawing of the central portion, which should be in alongitudinal direction, will react transversely of the blank to producea distortion thereof.

To avoid the result just described, I provide in my improved process,means for holding the marginal portions of the blank in such a mannerthat they are prevented on the one hand from wrinklingby any upsettingstresses, and o n the other hand are held from displacement laterally ofthe .blank under any drawing stress applied to the central -portionthereof. Various specific means may be employed for obtaining thisresult, but preferably that shown in Figs. l to 3, in which A is theblank and B B are hooked flanges bent from the opposite ed e portions.These flanges B B are forme primarily forobtaining a retainingengagement with the guides during the drawing operation, but they alsoperform a function in the fashioned article as a means of attachment tothe depending vertical flanges of the fender.

The flat blank being first formed with these reversely-bent edges, asshown in Fig. 3, is

then passed through a drawing machine coml In the drawings: Figure 1 isa longitudiriod of engagement with these rolls, as well as for a certaindistance before and after engagement, the hooks B and B are engaged withmarginal retaining guides E and E. These are so fashioned as to receivethe hooks of the blank and to hold the adjacent portion between parallelcontacting surfaces. This will prevent the drawing of the blank inwardand will also prevent the buckling of the margin portions under theinfluence of the bulging portion of the roll. The portion of each of theguides E and E beyond the rolls extends at an angle to the originalplane and is preferably curved to correspond to the longitudinal contourto be imparted to the product. It is not, however, necessary that thecontour of the guide should exactly conform to the contour of the nishedproduct, as the angleat the point of longitudinal bending is thecontrolling factor, and thus with the same guide variations in the curvemay `be produced by an angular adjustment with respect to the originalplane of the blank.

To facilitate the feeding of the blanks between the rolls C and D, acentral tongue F is formed at the entrance end, which may be morereadily deflected downward into engagement with the convex portion ofthe roll, and when thus engaged will draw the whole blank intoengagement. The opposite end of the blank may be correspondinglyrecessed at G, to permit the tongue of a following blank to engagetherewith, and the following blank will thus propel the advance blankuntil disengaged from the rolls and guides. Where the bulging contour iscomparatively flat, it is preferably held from distortion by a shoe Harranged adjacent to 'the delivery side of the rolls C and D. Tocomplete the article, it is necessary tov form the end portions thereof,and this is preferably accomplished by pressing between dies, such as Iand I', shown in Fig. 3. In

place of forming the blank with the hooked ianges at opposite edges, theblank may be attached to marginal guide strips J and J as shown in Fig.4, and these strips may be held from inward movement by abutting againstthe ends of the rolls or by any other suitable means.

What I claim asmy invention is 1. The method of fashioning sheet metalblanks to warped or transversely-curved forms, comprising theprogressive bulging of the central portion of the blank to stretch themetal longitudinally and transversely, and the holding of the marginalportions of the blank from inward movement during this operation toprevent buckling.l

2. Themethod of fashioning sheet metal blanks to warped ortransversely-curved forms, comprising the progressive bulging of thecentral portion of a sheet metal strip, and ther holding from inwardmovement and the guiding of the marginal portions of said strip toprevent buckling and to determine the longitudinal contour.

3. The method of fashioning sheet metal blanks to warped ortransversely-curved forms, comprising the formation of marginal flangeslongitudinally of the fiat sheet metal strip, the bending of said stripto bulge the central portion thereof, and the holding of the marginalportions during said bending movement to prevent drawing toward eachother and to hold the same from buckling.

4. The method of fashioning sheet metal .blanks to warped ortransverselycurved forms, comprising the forming of a sheet metal stripwith hooked flanges upon opposite edges thereof, feeding said striplongitudinally and simultaneously bulging the central portion thereof,the bending of the strip longitudinally during its feeding movement toconform to a predetermined curve,

and the guiding of the hooked flanges at the margin of said strip toprevent movement toward each other and to hold the same from buckling.

In testimony whereof I affix my signature in presence of two witnesses.I OTTO J. GROEHN.

Witnesses:

HARRY LUMPKIN, ARTHUR F. RoHRBACH.

